Method of manufacturing optical fiber, optical fiber manufacturing apparatus, and control apparatus therefor

ABSTRACT

A method of manufacturing an optical fiber of the invention includes: preparing a direction changer; drawing a bare optical fiber from an optical fiber preform, thereby forming the bare optical fiber; providing a coated layer made of a resin on a periphery of the bare optical fiber; obtaining an optical fiber by curing the coated layer; changing a direction of the bare optical fiber by use of the direction changer; measuring a drawing velocity of the optical fiber; and adjusting a length of the bare optical fiber from a drawing unit to a coating unit by controlling a position of the direction changer based on a measurement value of the drawing velocity, the drawing unit forming the bare optical fiber, the coating unit providing the coated layer on the periphery of the bare optical fiber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.15/017,776, filed on Feb. 8, 2016, claiming priority benefit from,claiming priority from Japanese Patent Application No. 2015-024648 filedon Feb. 10, 2015, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method of manufacturing an opticalfiber, an optical fiber manufacturing apparatus, and a control apparatusthat controls the manufacturing apparatus.

Description of the Related Art

Generally, in manufacture of an optical fiber, a method is employedwhich vertically and downwardly draws an optical fiber from an opticalfiber preform along a linear pathway.

The overall height of the system thereof is limited and becomes a factorthat affects the productivity of the manufacturing method.

Because the height of the system becomes a main factor that limits theproductivity, it is necessary to ensure the distance of a bare opticalfiber in the system which is required to sufficiently cool the bareoptical fiber obtained by drawing it from an optical fiber preform.

The above-described limitation can be eased by construction of newfacilities such as new buildings; however, a huge cost is necessary inorder to ease the limitation, if improvement in productivity is requiredin the future, it will be necessary to construct new facilities at greatexpense.

As a method of easing the limitation, a method of using a directionchanging device that includes a noncontact retention mechanism andchanges the direction in which a drawn fiber is drawn is known.

This noncontact retention mechanism is a mechanism that contactlesslyretains an object by using a pressure of fluid such as air, and adirection changer that is provided with this mechanism can change thedirection, in which a bare optical fiber (bare fiber) is drawn, withoutbeing in contact with the bare optical fiber.

By using this direction changer, the direction of a bare optical fiberwhich is fiber-drawn a optical fiber preform along a first pathway canbe changed into a direction along a second pathway (for example, referto Japanese Patent No. 5571958 and Japanese Unexamined PatentApplication, First Publication No. S62-003037).

Japanese Patent No. 5571958 discloses a method of manufacturing anoptical fiber, which uses a direction changing device that changes thedirection of a drawn fiber. The instrument has a groove into which anoptical fiber is to be introduced, and the groove has an opening formedtherein.

In this method, a gas that is introduced into the instrument isdischarged through one flow inlet port, and a direction of an opticalfiber is changed in a state where the optical fiber floats due to thepressure of the gas.

Japanese Unexamined Patent Application, First Publication No. S62-003037discloses a direction changer, the direction changer has a guide groovethat guides a bare optical fiber into, and gas outlet nozzles are formedon the bottom surface and both side surfaces of the guide groove (referto Example and FIGS. 3 and 4).

In this manufacturing method using the direction changer, a direction ofan optical fiber is changed due to the pressure of the gas blown fromfour outlet nozzles in a state where the optical fiber floats.

In order to stabilize an outer diameter (coating diameter) of a coatedlayer of an optical fiber, it is preferable to suitably control atemperature of a bare optical fiber.

According to the manufacturing methods disclosed in Japanese Patent No.5571958 and Japanese Unexamined Patent Application, First PublicationNo. S62-003037, since the bare optical fiber is retained by the gaspressure in the direction changing device, it is possible to control thetemperature of the bare optical fiber by use of the gas.

However, in the case of adjusting a temperature of the bare opticalfiber by control of the amount of gas in the direction changing device,there is the following problem.

Particularly, there is a concern that the amount of flotation of thebare optical fiber is insufficient and a bare optical fiber therebycomes into contact with the inner surface of the groove of the directionchanging device.

In the case where the bare optical fiber comes into contact with thedirection changing device, the bare optical fiber is damaged, and thereis a possibility that the strength of the bare optical fiber isdegraded.

SUMMARY OF THE INVENTION

Some aspects of the invention were conceived in view of theabove-described circumstances and have an object thereof to provide amethod of manufacturing an optical fiber, an optical fiber manufacturingapparatus, and a control apparatus that controls the manufacturingapparatus, which can sufficiently ensure an amount of flotation of abare optical fiber and can control a temperature of the bare opticalfiber with a high level of accuracy.

A first aspect of the invention provides a method of manufacturing anoptical fiber, including: preparing a direction changer, the directionchanger including a guide groove and an outlet nozzle, the guide groovebeing configured to guide a bare optical fiber, the bare optical fiberbeing arranged along and introduced into the guide groove, the outletnozzle being formed in the guide groove and being configured to causethe bare optical fiber to float; drawing the bare optical fiber from anoptical fiber preform, thereby forming the bare optical fiber (drawingstep); providing a coated layer made of a resin on a periphery of thebare optical fiber (coating step); obtaining an optical fiber by curingthe coated layer (curing step); changing the direction of the bareoptical fiber at a position between a position at which the bare opticalfiber is formed (the position in the drawing step, a bare-optical-fiberformation position) and a position at which the coated layer is providedon the periphery of the bare optical fiber (the position in the coatingstep, a coated-layer provision position) by use of the directionchanger; measuring an outer diameter of the coated layer; and adjustingthe length of the bare optical fiber from a drawing unit to a coatingunit by controlling the position of the direction changer based on ameasurement value of the outer diameter, the drawing unit forming thebare optical fiber, the coating unit providing the coated layer on theperiphery of the bare optical fiber.

A second aspect of the invention provides a method of manufacturing anoptical fiber, including: preparing a direction changer, the directionchanger including a guide groove and an outlet nozzle, the guide groovebeing configured to guide a bare optical fiber, the bare optical fiberbeing arranged along and introduced into the guide groove, the outletnozzle being formed in the guide groove and being configured to causethe bare optical fiber to float; drawing the bare optical fiber from anoptical fiber preform, thereby forming the bare optical fiber (drawingstep); providing a coated layer made of a resin on a periphery of thebare optical fiber (coating step); obtaining an optical fiber by curingthe coated layer (curing step); changing the direction of the bareoptical fiber at the position between the position at which the bareoptical fiber is formed (the position in the drawing step, abare-optical-fiber formation position) and the position at which thecoated layer is provided on the periphery of the bare optical fiber (theposition in the coating step, a coated-layer provision position) by useof the direction changer; measuring the drawing velocity of the opticalfiber; and adjusting the length of the bare optical fiber from a drawingunit to a coating unit by controlling the position of the directionchanger based on a measurement value of the drawing velocity, thedrawing unit forming the bare optical fiber, the coating unit providingthe coated layer on the periphery of the bare optical fiber.

A third aspect of the invention provides a method of manufacturing anoptical fiber, including: preparing a direction changer, the directionchanger including a guide groove and an outlet nozzle, the guide groovebeing configured to guide a bare optical fiber, the bare optical fiberbeing arranged along and introduced into the guide groove, the outletnozzle being formed in the guide groove and being configured to causethe bare optical fiber to float; drawing the bare optical fiber from anoptical fiber preform, thereby forming the bare optical fiber (drawingstep); providing a coated layer made of a resin on a periphery of thebare optical fiber (coating step); obtaining an optical fiber by curingthe coated layer (curing step); changing the direction of the bareoptical fiber at the position between the position at which the bareoptical fiber is formed (the position in the drawing step, abare-optical-fiber formation position) and the position at which thecoated layer is provided on the periphery of the bare optical fiber (theposition in the coating step, a coated-layer provision position) by useof the direction changer; measuring the temperature of the bare opticalfiber; and adjusting the length of the bare optical fiber from a drawingunit to a coating unit by controlling the position of the directionchanger based on a measurement value of the temperature, the drawingunit forming the bare optical fiber, the coating unit providing thecoated layer on the periphery of the bare optical fiber.

A fourth aspect of the invention provides a control apparatus used in anoptical fiber manufacturing apparatus, the manufacturing apparatusincluding: a drawing unit that forms a bare optical fiber by drawing thebare optical fiber from an optical fiber preform; a coating unit thatprovides a coated layer made of a resin on a periphery of the bareoptical fiber; and a curing unit that cures the coated layer, thecontrol apparatus including: one or more direction changers that changethe direction of the bare optical fiber at the position between thedrawing unit and the coating unit, each direction changer including aguide groove and an outlet nozzle, the guide groove being configured toguide the bare optical fiber, the bare optical fiber being arrangedalong and introduced into the guide groove, the outlet nozzle beingformed in the guide groove and being configured to cause the bareoptical fiber to float; a measurement unit that measures an outerdiameter of the coated layer; and a controller that adjusts the positionof the direction changers based on a measurement value of the outerdiameter measured by the measurement unit, the controller controllingpositions of the direction changers and thereby adjusting the length ofthe bare optical fiber from the drawing unit to the coating unit inaccordance with the measurement value.

A fifth aspect of the invention provides a control apparatus used in anoptical fiber manufacturing apparatus, the manufacturing apparatusincluding: a drawing unit that forms a bare optical fiber by drawing thebare optical fiber from an optical fiber preform; a coating unit thatprovides a coated layer made of a resin on a periphery of the bareoptical fiber; and a curing unit that cures the coated layer, thecontrol apparatus including: one or more direction changers that changethe direction of the bare optical fiber at the position between thedrawing unit and the coating unit, each direction changer including aguide groove and an outlet nozzle, the guide groove being configured toguide the bare optical fiber, the bare optical fiber being arrangedalong and introduced into the guide groove, the outlet nozzle beingformed in the guide groove and being configured to cause the bareoptical fiber to float; a measurement unit that measures the drawingvelocity of the optical fiber; and a controller that adjusts theposition of the direction changers based on a measurement value of thedrawing velocity measured by the measurement unit, the controllercontrolling positions of the direction changers and thereby adjustingthe length of the bare optical fiber from the drawing unit to thecoating unit in accordance with the measurement value.

A sixth aspect of the invention provides a control apparatus used in anoptical fiber manufacturing apparatus, the manufacturing apparatusincluding: a drawing unit that forms a bare optical fiber by drawing thebare optical fiber from an optical fiber preform; a coating unit thatprovides a coated layer made of a resin on a periphery of the bareoptical fiber; and a curing unit that cures the coated layer, thecontrol apparatus including: one or more direction changers that changethe direction of the bare optical fiber at the position between thedrawing unit and the coating unit, each direction changer including aguide groove and an outlet nozzle, the guide groove being configured toguide the bare optical fiber, the bare optical fiber being arrangedalong and introduced into the guide groove, the outlet nozzle beingformed in the guide groove and being configured to cause the bareoptical fiber to float; a measurement unit that measures a temperatureof the bare optical fiber; and a controller that adjusts the position ofthe direction changers based on a measurement value of the temperaturemeasured by the measurement unit, the controller controlling positionsof the direction changers and thereby adjusting the length of the bareoptical fiber from the drawing unit to the coating unit in accordancewith the measurement value.

A seventh aspect of the invention provides an optical fibermanufacturing apparatus including: a control apparatus according to theabove-described fourth aspect; a drawing unit that forms a bare opticalfiber by drawing the bare optical fiber from an optical fiber preform; acoating unit that provide a coated layer made of a resin on a peripheryof the bare optical fiber; and a curing unit that cures the coatedlayer.

An eighth aspect of the invention provides an optical fibermanufacturing apparatus including: a control apparatus according to theabove-described fifth aspect; a drawing unit that forms a bare opticalfiber by drawing the bare optical fiber from an optical fiber preform; acoating unit that provide a coated layer made of a resin on a peripheryof the bare optical fiber; and a curing unit that cures the coatedlayer.

A ninth aspect of the invention provides an optical fiber manufacturingapparatus including: a control apparatus according to theabove-described sixth aspect; a drawing unit that forms a bare opticalfiber by drawing the bare optical fiber from an optical fiber preform; acoating unit that provide a coated layer made of a resin on a peripheryof the bare optical fiber; and a curing unit that cures the coatedlayer.

Effects of the Invention

According to the aspects of the invention, since the path length of thebare optical fiber is adjusted by controlling the position of thedirection changer based on a measurement value of an outer diameter ofthe coated layer an optical fiber production intermediate, thetemperature of the bare optical fiber which is introduced into thecoating unit is adjusted with a high level of accuracy, and it ispossible to maintain the outer diameter of the coated layer within aconstant range in the coating unit.

According to the aspects of the invention, since it is possible toadjust the temperature of the bare optical fiber without varying theflow rate of the gas discharged from the outlet nozzle in the directionchanger, it is possible to avoid the bare optical fiber from being incontact with the inner side surface of the guide groove due to a lack offlotation of the bare optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the configuration of an opticalfiber manufacturing apparatus according to a first embodiment of theinvention.

FIG. 2 is a cross-sectional schematic diagram showing the structure of adirection changer of the manufacturing apparatus shown in FIG. 1.

FIG. 3 is a front view showing a first example of the direction changer.

FIG. 4 is a front view showing a modified example of the directionchanger of the first example shown in FIG. 3.

FIG. 5 is a front view showing a second example of the directionchanger.

FIG. 6 is a front view showing a modified example of the directionchanger of the second example shown in FIG. 5.

FIG. 7 is a schematic diagram showing the configuration of an opticalfiber manufacturing apparatus according to a second embodiment of theinvention.

FIG. 8 is a schematic diagram showing the configuration of an opticalfiber manufacturing apparatus according to a third embodiment of theinvention.

FIG. 9 is a schematic diagram showing the configuration of an opticalfiber manufacturing apparatus according to a fourth embodiment of theinvention.

FIG. 10 is a schematic diagram showing the configuration of an opticalfiber manufacturing apparatus according to a fifth embodiment of theinvention.

FIG. 11 is a schematic diagram showing the configuration of an opticalfiber manufacturing apparatus according to a sixth embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram showing the configuration of amanufacturing apparatus 1A which serves as an optical fibermanufacturing apparatus according to a first embodiment of theinvention.

The manufacturing apparatus 1A includes a drawing unit 10, directionchangers 20 (20A, 20B, 20C), a coating unit 30, a curing unit 40, ameasurement unit 50, a controller 60, a pick-up unit 70, a pulley 80,and a winding unit 90.

The direction changers 20, the measurement unit 50, and the controller60 constitute a control apparatus 101.

The drawing unit 10 is provided with a heating furnace 11, an opticalfiber preform 2 is heated by the heating furnace 11, and a bare opticalfiber 3 is formed by drawing the heated preform.

The direction changers 20 change a direction of the bare optical fiber3.

Three direction changers 20 are used in the manufacturing apparatus 1A.

The direction changers 20 are each referred to as a first directionchanger 20A, a second direction changer 20B, and a third directionchanger 20C in order from the upstream side to the downstream side inthe fiber drawing direction.

The first direction changer 20A changes, by 90 degrees, the direction ofthe bare optical fiber 3 that is drawn from the optical fiber preform 2in the downward vertical direction (first pathway L1), as a result, thedirection of the bare optical fiber 3 is in the horizontal direction(second pathway L2).

A plane including the first pathway L1 and the second pathway L2 isreferred to as P1.

The X-direction is the direction extending in the second pathway L2 inthe plane P1 and the Y-direction is the direction perpendicular to theplane P1.

The second direction changer 20B changes the direction of the bareoptical fiber 3 by 180 degrees, as a result, the direction of the bareoptical fiber 3 is directed to the direction (third pathway L3) oppositeto the second pathway L2.

The second direction changer 20B is movable in the direction in whichthe second direction changer comes close to or separates from the firstdirection changer 20A and the third direction changer 20C.

Particularly, the second direction changer 20B is movable in theX-direction.

The second direction changer 20B can move along a guide rail thatextends in, for example, the X-direction by use of a driving device suchas a motor.

The third direction changer 20C changes the direction of the bareoptical fiber 3 by 90 degrees, as a result, the direction of the bareoptical fiber 3 is in the downward vertical direction (fourth pathwayL4).

The coating unit 30 is configured to coat (coating) the periphery of thebare optical fiber 3 with a coating material such as a urethaneacrylate-based resin, thereby forms a coated layer, and an optical fiberproduction intermediate 4 is obtained.

The resin coating is, for example, a bilayer coating such that amaterial used to form a first coated layer having a lower Young'smodulus is applied to the inside thereof and a material used to form asecond coated layer having a higher Young's modulus is applied to theoutside thereof.

The material used to form the resin coating is, for example, anultraviolet curable resin.

The coating unit 30 may be configured to independently apply the firstcoated layer and the second coated layer or may be configured tosimultaneously apply the first coated layer and the second coated layer.

The curing unit 40 is provided with one or more UV lamps 40 a, isconfigured to cure the coated layer of the optical fiber productionintermediate 4 and thereby form an optical fiber 5.

For example, the curing unit 40 includes UV lamps 40 a which form aplurality of pairs thereof and are provided to sandwich spaces throughwhich the optical fiber production intermediate 4 passes.

The measurement unit 50 can measure an outer diameter of the coatedlayer of the optical fiber production intermediate 4.

It is preferable that the measurement unit 50 can measure an outerdiameter of the coated layer without coming in contact with the opticalfiber production intermediate 4.

As the measurement unit 50, for example, a measurement device thatincludes a light source and a detector can be used.

By use of this measurement device, the light source (laser light source,or the like) that is provided at, for example, the side position of theoptical fiber production intermediate 4 emits light thereto, thedetector that is disposed to face the light source receivesforward-scattered light from the optical fiber production intermediate,and an outer diameter of the optical fiber production intermediate 4(that is, an outer diameter of the coated layer) is measured byanalyzing a pattern of the received light or the intensity thereof.

The measurement unit 50 can be provided between the coating unit 30 andthe curing unit 40.

The measurement unit 50 outputs a measurement signal to the controller60 based on the measurement value of the outer diameter.

The controller 60 can control the position of the second directionchanger 20B (position in the X-direction) based on the measurementsignal output from the measurement unit 50.

The controller 60 controls driving or stopping of, for example, theabove-described driving device such as a motor and thereby can determinethe position of the second direction changer 20B in the X-direction.

The optical fiber 5 is picked up by the pick-up unit 70, the pulley 80changes the direction of the optical fiber, and the optical fiber iswound around the winding unit 90.

The pick-up unit 70 is, for example, a pick-up capstan, and the pick-upunit determines the drawing speed.

The drawing speed is greater than or equal to, for example, 1500 m/min.

The winding unit 90 is a bobbin that winds the optical fiber 5therearound.

The outer diameter of the optical fiber preform 2 is greater than orequal to, for example, 100 mm, and the length of the optical fiber 5manufactured from the optical fiber preform 2 is, for example, severalthousands km.

Hereinbelow, configurations of a direction changer 20 will be described.

As shown in FIG. 3, a direction changer 201 is a first example of thedirection changer 20 and can change a direction of the bare opticalfiber 3 by 90 degrees.

The direction changer 201 is formed in a quarter-circular shape (arc) inplan view and has an outer peripheral face 20 a and a guide groove 21.The guide groove 21 is formed on and along the entire periphery of theouter peripheral face 20 a.

The center of the direction changer 201 coincides with the Y-direction,and the direction changer 201 is provided in the attitude in which theradial direction D1 (refer to FIG. 2) is in the direction along theplane P1 (refer to FIG. 1).

Here, the direction along the outer peripheral face 20 a formed in acircular-arc shape in plan view is referred to as a circumferentialdirection.

An outlet nozzle 22 is formed at the bottom of the guide groove 21 andalong the guide groove 21. The outlet nozzle blows fluid (e.g., air)into the guide groove, and the fluid (e.g., air) causes the bare opticalfiber 3 which is arranged along and introduced into the guide groove 21to float.

The outlet nozzle 22 is formed over the entire guide groove 21.

A first end 22 a (one end) of the outlet nozzle 22 reaches a first end21 a (one end) of the guide groove 21, and a second end 22 b (the otherend) of the outlet nozzle 22 reaches a second end 21 b (the other end)of the guide groove 21.

As shown in FIG. 2, the direction changer 201 is configured to be ableto discharge fluid (for example, air) of the space (fluid reservoir 25)into the guide groove 21 through the outlet nozzle 22. The space isensured in the direction changer 201.

The direction changer 201 can be configured to introduce the fluid intothe fluid reservoir 25 from, for example, the outside and discharge thefluid into the guide groove 21 through the outlet nozzle 22.

It is preferable that the guide groove 21 be formed to be inclined withrespect to the radial direction D1 so that the space (length in theY-direction) between the inner side surfaces 21 c thereof graduallyincreases in the radial-outer direction.

It is preferable that the inclination angles θ1 of the two inner sidesurfaces 21 c with respect to the radial direction D1 are equal to eachother.

In the direction changer 201 shown in FIG. 3, the bare optical fiber 3enters the first end 21 a of the guide groove 21 that is formed in aquarter-circular shape (arc) and exits from the second end 21 b, and thedirection of the bare optical fiber is thereby changed by 90 degrees.

A fiber inlet portion 23 to which the bare optical fiber 3 enters is aportion including the first end 21 a of the guide groove 21, and a fiberoutlet portion 24 from which the bare optical fiber 3 exits is a portionincluding the second end 21 b of the guide groove 21.

A direction changer 202 shown in FIG. 4 is a modified example of thedirection changer 201 and is formed in a three-quarter-circular shape(arc) in plan view.

Hereinbelow, identical reference numerals are used for the elementswhich are identical to those of the above description, and theexplanations thereof are simplified here.

The direction changer 202 is configured to include: a body part 29 ahaving the same structure as that of the direction changer 201 shown inFIG. 3; and auxiliary parts 29 b and 29 c, each of which has the samestructure as that of the body part 29 a and which are consecutivelyconnected to the incoming side and the outgoing side of the body part 29a.

Regarding the direction changer 202, the bare optical fiber 3 enters theguide groove 21 of the body part 29 a through the fiber inlet portion23′, the direction of the bare optical fiber is changed by 90 degrees bythe body part 29 a, thereafter, the bare optical fiber exits from thebody part through the fiber outlet portion 24′. Therefore, the basicfunction of the direction changer 202 is the same as that of thedirection changer 201.

The direction changers 201 and 202 can change the direction of the bareoptical fiber 3 by 90 degrees, and therefore can be used as the firstdirection changer 20A and the third direction changer 20C as shown inFIG. 1.

A direction changer 203 shown in FIG. 5 is a second example of thedirection changer 20 and can change the direction of the bare opticalfiber 3 by 180 degrees.

The direction changer 203 is formed in a semicircular shape in plan viewand has an outer peripheral face 20 a and a guide groove 31. The guidegroove 31 is formed on and along the entire periphery of the outerperipheral face 20 a.

An outlet nozzle 32 is formed at the bottom of the guide groove 31 andalong the guide groove 31. The outlet nozzle blows fluid (e.g., air)into the guide groove, and the fluid (e.g., air) causes the bare opticalfiber 3 to float.

The outlet nozzle 32 is formed over the entire guide groove 31.

The direction changer 203 is configured to be able to discharge fluidinto the guide groove 31 through the outlet nozzle 32 from a fluidreservoir 35.

In the direction changer 203, the bare optical fiber 3 enters a firstend 31 a (one end) of the guide groove 31 of the semicircular shape andexits from a second end 31 b (the other end) thereof, and the directionof the bare optical fiber is changed by 180 degrees.

A fiber inlet portion 33 is a portion including the second end 31 a ofthe guide groove 31, and a fiber outlet portion 34 is a portionincluding the second end 31 b of the guide groove 31.

The cross-sectional configuration of the guide groove 31 is the same asthat of the guide groove 21 (refer to FIG. 2).

A direction changer 204 shown in FIG. 6 is a modified example of thedirection changer 203 and is formed in a three-quarter-circular shape(arc) in plan view.

The direction changer 204 is configured to include: a body part 39 ahaving the same structure as that of the direction changer 203 shown inFIG. 5; and auxiliary parts 39 b and 39 c, each of which has the samecross-sectional structure as that of the body part 39 a, which areconsecutively connected to the incoming side and the outgoing side ofthe body part 39 a, and which are formed in a one-eighth circular shape(arc) in plan view.

Regarding the direction changer 204, the bare optical fiber 3 enters theguide groove 31 of the body part 39 a through the fiber inlet portion33′, the direction of the bare optical fiber is changed by 180 degreesby the body part 39 a, thereafter, the bare optical fiber exits from thebody part through the fiber outlet portion 34′. Therefore, the basicfunction of the direction changer 204 is the same as that of thedirection changer 203.

The direction changers 203 and 204 can change the direction of the bareoptical fiber 3 by 180 degrees, and therefore can be used as the firstdirection changer 20B as shown in FIG. 1.

Next, a method according to a first embodiment of the invention will bedescribed which manufactures an optical fiber in the case of using, forexample, the manufacturing apparatus 1A.

(Drawing Step)

In the drawing unit 10, the optical fiber preform 2 is heated and drawn,and the bare optical fiber 3 is formed.

(Direction Change by use of Direction Changer)

The direction of the bare optical fiber 3 that is drawn from the opticalfiber preform 2 in the downward vertical direction (first pathway L1) ischanged by 90 degrees by the first direction changer 20A, as a result,the direction of the bare optical fiber 3 is in the horizontal direction(second pathway L2).

The direction of the bare optical fiber 3 is changed by 180 degrees bythe second direction changer 20B, as a result, the direction of the bareoptical fiber 3 is directed to the direction (third pathway L3) oppositeto the second pathway L2. The direction of the bare optical fiber 3 ischanged by 90 degrees by the third direction changer 20C, as a result,the direction of the bare optical fiber 3 is in the downward verticaldirection (fourth pathway L4).

In the direction changers 20A to 20C, as a result of discharging thefluid (for example, air) in the fluid reservoir 25 into the guide groove21 through the outlet nozzle 22, it is possible to cause the bareoptical fiber 3 to float.

Particularly, as shown in FIG. 2, since a difference in pressure betweena deep portion 21 d of the guide groove 21 and a shallow portion 21 ethereof increases due to the discharged air, a force in the radial-outerdirection of the direction changer is applied to the bare optical fiber3, and the bare optical fiber 3 floats.

(Coating Step)

In the coating unit 30, the optical fiber production intermediate 4 isobtained by forming a coated layer by applying a coating material suchas a urethane acrylate based resin onto the periphery of the bareoptical fiber 3.

(Curing Step)

In the curing unit 40, the coated layer of the optical fiber productionintermediate 4 is cured by irradiating the coating material with UVlight by the UV lamp 40 a or the like, and the optical fiber 5 isthereby formed.

(Adjustment of Path Length of Bare Optical Fiber 3)

The measurement unit 50 measures an outer diameter of the optical fiberproduction intermediate 4 (i.e., an outer diameter of the coated layer)and outputs a measurement signal to the controller 60 based on themeasurement value.

The controller 60 controls the position of the second direction changer20B in accordance with the measurement value of the outer diameter andthereby adjusts the path length of the bare optical fiber 3.

The path length of the bare optical fiber 3 is the length of the bareoptical fiber 3 from the drawing unit 10 to the coating unit 30.

Particularly, in the case where the outer diameter of the coated layerincreases, the controller 60 outputs a measurement signal correspondingto the measurement value, and the controller 60 disposes the seconddirection changer 20B at a position close to the first direction changer20A and the third direction changer 20C.

As a control method, feedback control such as PID control is preferable.

Accordingly, it is possible to carry out control of the position of thesecond direction changer 20B with a high degree of responsiveness.

When the second direction changer 20B approaches the first directionchanger 20A and the third direction changer 20C, since the path lengthof the bare optical fiber 3 decreases accordingly, the temperature ofthe bare optical fiber 3 which is introduced into the coating unit 30relatively increases.

In the case where the temperature of the bare optical fiber 3 increases,since the thickness of the coated layer formed in the coating unit 30decreases due to physical properties of the coating material, the outerdiameter of the coated layer decreases.

On the other hand, in the case where the outer diameter of the coatedlayer decreases, the controller 60 outputs a measurement signalcorresponding to the measurement value, and the controller 60 disposesthe second direction changer 20B at the position apart from the firstdirection changer 20A and the third direction changer 20C.

When the second direction changer 20B moves separately from the firstdirection changer 20A and the third direction changer 20C, since thepath length of the bare optical fiber 3 increases accordingly, thetemperature of the bare optical fiber 3 which is introduced into thecoating unit 30 relatively decreases.

In the case where the temperature of the bare optical fiber 3 decreases,since the thickness of the coated layer formed in the coating unit 30increases, the outer diameter of the coated layer increases.

The optical fiber 5 is picked up by the pick-up unit 70, the directionof the optical fiber 5 is changed by the pulley 80, and the opticalfiber 5 is wound around the winding unit 90.

According to the manufacturing method, since the path length of the bareoptical fiber 3 is adjusted by controlling the position of the seconddirection changer 20B based on the measurement value of the outerdiameter of the coated layer of the optical fiber productionintermediate 4, the temperature of the bare optical fiber 3 which isintroduced into the coating unit 30 is adjusted with a high level ofaccuracy, and it is possible to maintain the outer diameter of thecoated layer within a constant range in the coating unit 30.

According to the manufacturing method, it is possible to adjust thetemperature of the bare optical fiber 3 without varying the flow rate ofthe gas discharged from the outlet nozzle 22 in the direction changers20A to 20C.

Therefore, it is possible to avoid the bare optical fiber 3 from beingin contact with the inner side surface 21 c of the guide groove 21 dueto a lack of flotation of the bare optical fiber.

FIG. 7 is a schematic diagram showing the configuration of amanufacturing apparatus 1B which serves as an optical fibermanufacturing apparatus according to a second embodiment of theinvention. In FIG. 7, identical reference numerals are used for theelements which are identical to those of the above-described embodiment,and the explanations thereof are omitted or simplified here.

The manufacturing apparatus 1B includes the drawing unit 10, thedirection changers 20 (20A, 20B, 20C), the coating unit 30, the curingunit 40, a controller 100, the pick-up unit 70, the pulley 80, and thewinding unit 90.

The direction changers 20, the pick-up unit 70, and the controller 100constitute a control apparatus 102.

The pick-up unit 70 serves as a measurement unit that measures a drawingvelocity of the optical fiber 5.

The controller 100 can control the position of the second directionchanger 20B (position in the X-direction) based on the measurementsignal output from the pick-up unit 70.

Next, a method according to a second embodiment of the invention will bedescribed which manufactures an optical fiber in the case of using, forexample, the manufacturing apparatus 1B.

The drawing step, the direction change by use of the direction changer,the coating step, and the curing step are the same as those of theabove-described embodiments.

(Adjustment of Path Length of Bare Optical Fiber 3)

The pick-up unit 70 measures a drawing velocity of the optical fiber 5and outputs a measurement signal to the controller 100 based on themeasurement value.

The controller 100 controls the position of the second direction changer20B in accordance with the measurement value of the drawing velocity andthereby adjusts the path length of the bare optical fiber 3.

Particularly, in the case where the drawing velocity of the opticalfiber 5 decreases, the controller 100 outputs a measurement signalcorresponding to the measurement value, and the controller 100 disposesthe second direction changer 20B at a position close to the firstdirection changer 20A and the third direction changer 20C.

As a control method, proportional control is preferable.

When the second direction changer 20B approaches the first directionchanger 20A and the third direction changer 20C, since the path lengthof the bare optical fiber 3 decreases accordingly, the temperature ofthe bare optical fiber 3 which is introduced into the coating unit 30relatively increases.

In the case where the temperature of the bare optical fiber 3 increases,since the thickness of the coated layer formed in the coating unit 30decreases due to physical properties of the coating material, the outerdiameter of the coated layer decreases.

On the other hand, in the case where the drawing velocity of the opticalfiber 5 increases, the controller 100 outputs a measurement signalcorresponding to the measurement value, and the controller 100 disposesthe second direction changer 20B at the position apart from the firstdirection changer 20A and the third direction changer 20C.

When the second direction changer 20B moves separately from the firstdirection changer 20A and the third direction changer 20C, since thepath length of the bare optical fiber 3 increases accordingly, thetemperature of the bare optical fiber 3 which is introduced into thecoating unit 30 relatively decreases.

In the case where the temperature of the bare optical fiber 3 decreases,since the thickness of the coated layer formed in the coating unit 30increases, the outer diameter of the coated layer increases.

According to the manufacturing method, since the path length of the bareoptical fiber 3 is adjusted by controlling the position of the seconddirection changer 20B based on the measurement value of the drawingvelocity of the optical fiber 5, it is possible to maintain the outerdiameter of the coated layer within a constant range in the coating unit30.

According to the manufacturing method, since it is possible to adjustthe temperature of the bare optical fiber 3 in the direction changers20A to 20C without varying the flow rate of the gas, it is possible toavoid the bare optical fiber 3 from being in contact with the inner sidesurface 21 c of the guide groove 21 due to a lack of flotation of thebare optical fiber.

FIG. 8 is a schematic diagram showing the configuration of amanufacturing apparatus 1C which serves as an optical fibermanufacturing apparatus according to a third embodiment of theinvention. In FIG. 8, identical reference numerals are used for theelements which are identical to those of the above-describedembodiments, and the explanations thereof are omitted or simplifiedhere.

The manufacturing apparatus 1C includes the drawing unit 10, thedirection changers 20 (20A, 20B, 20C), the coating unit 30, the curingunit 40, a measurement unit 110, a controller 120, the pick-up unit 70,the pulley 80, and the winding unit 90.

The direction changers 20, the measurement unit 110, and the controller120 constitute a control apparatus 103.

The manufacturing apparatus 1C is different from the manufacturingapparatus 1A shown in FIG. 1 in that the measurement unit 110 whichmeasures a temperature of the bare optical fiber 3 is used instead ofthe measurement unit 50 which measures an outer diameter of the coatedlayer.

It is preferable that the measurement unit 110 can measure a temperatureof the bare optical fiber 3 without coming in contact with the bareoptical fiber 3.

The measurement unit 110 is, for example, a radiation thermometer.

The measurement unit 110 can be provided between the third directionchanger 20C and the coating unit 30.

The controller 120 can control the position of the second directionchanger 20B (position in the X-direction) based on the measurementsignal output from the measurement unit 110.

Next, a method according to a third embodiment of the invention will bedescribed which manufactures an optical fiber in the case of using, forexample, the manufacturing apparatus 1C.

The drawing step, the direction change by use of the direction changer,the coating step, and the curing step are the same as those of theabove-described embodiments.

(Adjustment of Path Length of Bare Optical Fiber 3)

The measurement unit 110 measures a temperature of the bare opticalfiber 3 and outputs a measurement signal to the controller 120 based onthe measurement value.

The controller 120 controls the position of the second direction changer20B in accordance with the measurement value of the temperature andthereby adjusts the path length of the bare optical fiber 3.

Particularly, in the case where the temperature of the optical fiberproduction intermediate 4 decreases, the controller 120 outputs ameasurement signal corresponding to the measurement value, and thecontroller 120 disposes the second direction changer 20B at a positionclose to the first direction changer 20A and the third direction changer20C.

As a control method, feedback control such as PID control is preferable.

When the second direction changer 20B approaches the first directionchanger 20A and the third direction changer 20C, since the path lengthof the bare optical fiber 3 decreases accordingly, the temperature ofthe bare optical fiber 3 which is introduced into the coating unit 30relatively increases.

In the case where the temperature of the bare optical fiber 3 increases,since the thickness of the coated layer formed in the coating unit 30decreases, the outer diameter of the coated layer decreases.

On the other hand, in the case where the temperature of the opticalfiber production intermediate 4 increases, the controller 120 outputs ameasurement signal corresponding to the measurement value, andcontroller 120 disposes the second direction changer 20B at the positionapart from the first direction changer 20A and the third directionchanger 20C.

When the second direction changer 20B moves separately from the firstdirection changer 20A and the third direction changer 20C, since thepath length of the bare optical fiber 3 increases accordingly, thetemperature of the bare optical fiber 3 which is introduced into thecoating unit 30 relatively decreases.

In the case where the temperature of the bare optical fiber 3 decreases,since the thickness of the coated layer formed in the coating unit 30increases, the outer diameter of the coated layer increases.

According to the manufacturing method, since the path length of the bareoptical fiber 3 is adjusted by controlling the position of the seconddirection changer 20B based on the measurement value of the temperatureof the optical fiber production intermediate 4, it is possible tomaintain the outer diameter of the coated layer within a constant rangein the coating unit 30.

According to the manufacturing method, since it is possible to adjustthe temperature of the bare optical fiber 3 in the direction changers20A to 20C without varying the flow rate of the gas, it is possible toavoid the bare optical fiber 3 from being in contact with the inner sidesurface 21 c of the guide groove 21 due to a lack of flotation of thebare optical fiber.

FIG. 9 is a schematic diagram showing the configuration of amanufacturing apparatus 1D which serves as an optical fibermanufacturing apparatus according to a fourth embodiment of theinvention. In FIG. 9, identical reference numerals are used for theelements which are identical to those of the above-describedembodiments, and the explanations thereof are omitted or simplifiedhere.

The manufacturing apparatus 1D includes the drawing unit 10, thedirection changers 20 (20A, 20B, 20D, 20E, 20F), the coating unit 30,the curing unit 40, a measurement unit 50, a controller 130, the pick-upunit 70, the pulley 80, and the winding unit 90.

The direction changers 20, the measurement unit 50, and the controller130 constitute a control apparatus 104.

The manufacturing apparatus 1D is different from the manufacturingapparatus 1A shown in FIG. 1 in that the manufacturing apparatus 1Dincludes a third direction changer 20D, a fourth direction changer 20E,and a fifth direction changer 20F.

The third direction changer 20D changes the direction of the bareoptical fiber 3 extending in the horizontal direction (third pathway L3)by 180 degrees, as a result, the direction of the bare optical fiber 3is directed to the direction (fourth pathway L5) opposite to the thirdpathway L3.

The fourth direction changer 20E changes the direction of the bareoptical fiber 3 by 180 degrees, as a result, the direction of the bareoptical fiber 3 is directed to the direction (fifth pathway L6) oppositeto the fourth pathway L5.

The fourth direction changer 20E is movable in the direction in whichthe fourth direction changer comes close to or separates from the thirddirection changer 20D and the fifth direction changer 20F.

Particularly, the fourth direction changer 20E is movable in theX-direction.

The fourth direction changer 20E can move along a guide rail thatextends in, for example, the X-direction by use of a driving device suchas a motor.

The fifth direction changer 20F changes the direction of the bareoptical fiber 3 by 90 degrees, as a result, the direction of the bareoptical fiber 3 is in the downward vertical direction (sixth pathwayL7).

The controller 130 can control the position of the second directionchanger 20B and the fifth direction changer 20E (position in theX-direction) based on the measurement signal output from the measurementunit 50.

Next, a method according to a fourth embodiment of the invention will bedescribed which manufactures an optical fiber in the case of using, forexample, the manufacturing apparatus 1D.

(Direction Change by use of Direction Changer)

The direction of the bare optical fiber 3 that is drawn from the opticalfiber preform 2 in the downward vertical direction (first pathway L1) ischanged by 90 degrees by the first direction changer 20A, as a result,the direction of the bare optical fiber 3 is in the horizontal direction(second pathway L2).

The direction of the bare optical fiber 3 is changed by 180 degrees bythe second direction changer 20B, as a result, the direction of the bareoptical fiber 3 is directed to the direction (third pathway L3) oppositeto the second pathway L2. The direction of the bare optical fiber 3 ischanged by 180 degrees by the third direction changer 20D, as a result,the direction (fourth pathway L5) opposite to the third pathway L3.

The direction of the bare optical fiber 3 is changed by 180 degrees bythe fourth direction changer 20E, as a result, the direction of the bareoptical fiber 3 is directed to the direction (fifth pathway L6) oppositeto the fourth pathway L5. The direction of the bare optical fiber 3 ischanged by 90 degrees by the fifth direction changer 20F, as a result,the direction of the bare optical fiber 3 is in the downward verticaldirection (sixth pathway L7).

(Adjustment of Path Length of Bare Optical Fiber 3)

The measurement unit 50 measures an outer diameter of the optical fiberproduction intermediate 4 (i.e., an outer diameter of the coated layer)and outputs a measurement signal to the controller 130 based on themeasurement value.

The controller 130 controls the positions of the second directionchanger 20B and the fourth direction changer 20E in accordance with themeasurement value of the outer diameter and thereby adjusts the pathlength of the bare optical fiber 3.

As a control method, feedback control such as PID control is preferable.

Particularly, in the case where the outer diameter of the coated layerof the optical fiber production intermediate 4 increases, the controller130 disposes the second direction changer 20B and the fourth directionchanger 20E at the positions close to the direction changers 20A, 20D,and 20F. In the case where the outer diameter of the coated layer of theoptical fiber production intermediate 4 decreases, the controller 130disposes the second direction changer 20B and the fourth directionchanger 20E at the positions apart from the direction changers 20A, 20D,and 20F.

According to the manufacturing method, since the path length of the bareoptical fiber 3 is adjusted by controlling the positions of the seconddirection changer 20B and the fourth direction changer 20E, thevariation range in the path length of the bare optical fiber 3increases.

Consequently, it is possible to carry out adjustment of the outerdiameter of the coated layer with a high degree of responsiveness.

According to the manufacturing method, since it is possible to adjustthe temperature of the bare optical fiber 3 in the direction changers20A to 20F without varying the flow rate of the gas, it is possible toavoid the bare optical fiber 3 from being in contact with the inner sidesurface 21 c of the guide groove 21 due to a lack of flotation of thebare optical fiber.

FIG. 10 is a schematic diagram showing the configuration of amanufacturing apparatus 1E which serves as an optical fibermanufacturing apparatus according to a fifth embodiment of theinvention. In FIG. 10, identical reference numerals are used for theelements which are identical to those of the above-described embodiment,and the explanations thereof are omitted or simplified here.

The manufacturing apparatus 1E includes the drawing unit 10, thedirection changers 20 (20A, 20B, 20D, 20E, 20F), the coating unit 30,the curing unit 40, a controller 140, the pick-up unit 70, the pulley80, and the winding unit 90.

The direction changers 20, the controller 140, and the pick-up unit 70constitute a control apparatus 105.

The controller 140 can controls the positions of the second directionchanger 20B and the fourth direction changer 20E (position in theX-direction) based on the measurement signal output from the pick-upunit 70.

Next, a method according to a fifth embodiment of the invention will bedescribed which manufactures an optical fiber in the case of using, forexample, the manufacturing apparatus 1E.

(Adjustment of Path Length of Bare Optical Fiber 3)

The pick-up unit 70 measures a drawing velocity of the optical fiber 5and outputs a measurement signal to the controller 140 based on themeasurement value.

The controller 140 controls the positions of the second directionchanger 20B and the fourth direction changer 20E in accordance with themeasurement value of the drawing velocity and thereby adjusts the pathlength of the bare optical fiber 3.

Particularly, in the case where the drawing velocity of the opticalfiber 5 decreases, the controller 140 and disposes the second directionchanger 20B and the fourth direction changer 20E at the positions closeto the direction changers 20A, 20D, and 20F. In the case where thedrawing velocity of the optical fiber 5 increases, the controller 140disposes the second direction changer 20B and the fourth directionchanger 20E at the positions apart from the direction changers 20A, 20D,and 20F.

According to the manufacturing method, since the path length of the bareoptical fiber 3 is adjusted by controlling the positions of the seconddirection changer 20B and the fourth direction changer 20E based on themeasurement value of the drawing velocity of the optical fiber 5, it ispossible to maintain the outer diameter of the coated layer within aconstant range in the coating unit 30.

According to the manufacturing method, since it is possible to adjustthe temperature of the bare optical fiber 3 in the direction changers20A to 20F without varying the flow rate of the gas, it is possible toavoid the bare optical fiber 3 from being in contact with the inner sidesurface 21 c of the guide groove 21 due to a lack of flotation of thebare optical fiber.

FIG. 11 is a schematic diagram showing the configuration of amanufacturing apparatus 1F which serves as an optical fibermanufacturing apparatus according to a sixth embodiment of theinvention. In FIG. 11, identical reference numerals are used for theelements which are identical to those of the above-described embodiment,and the explanations thereof are omitted or simplified here.

The manufacturing apparatus 1F includes the drawing unit 10, thedirection changers 20 (20A, 20G, 20H, 20I, 20J), the coating unit 30,the curing unit 40, the measurement unit 50, a controller 150, thepick-up unit 70, the pulley 80, and the winding unit 90.

The direction changers 20, the measurement unit 50, the controller 150constitute a control apparatus 106.

The manufacturing apparatus 1F is different from the manufacturingapparatus 1A shown in FIG. 1 in that the manufacturing apparatus 1Fincludes a second direction changer 20G, a third direction changer 20H,a fourth direction changer 20I, and a fifth direction changer 20Jinstead of the second direction changer 20B and the third directionchanger 20C.

The second direction changer 20G changes, by 90 degrees, the bareoptical fiber 3 that is in the horizontal direction (second pathway L8)by the first direction changer 20A, as a result, the direction of thebare optical fiber 3 is in the upward vertical direction (third pathwayL9).

The third direction changer 20H changes the direction of the bareoptical fiber 3 by 180 degrees, as a result, the direction of the bareoptical fiber 3 is in the downward vertical direction (fourth pathwayL10) opposite to the third pathway L9.

The third direction changer 20H is movable in the direction in which thethird direction changer comes close to or separates from the seconddirection changer 20G and the fourth direction changer 20I.

Particularly, the third direction changer 20H is movable in the verticaldirection.

The fourth direction changer 201 changes the direction of the bareoptical fiber 3 by 90 degrees, as a result, the direction of the bareoptical fiber 3 is in the horizontal direction (fifth pathway L11).

The fifth direction changer 20J changes the direction of the bareoptical fiber 3 by 90 degrees, as a result, the direction of the bareoptical fiber 3 is in the downward vertical direction (sixth pathwayL12).

The controller 150 can control the position of the third directionchanger 20H (position in Z-direction) based on the measurement signaloutput from the measurement unit 50.

The Z-direction is perpendicular to both the X-direction and theY-direction.

Next, a method according to a sixth embodiment of the invention will bedescribed which manufactures an optical fiber in the case of using, forexample, the manufacturing apparatus 1F.

(Direction Change by use of Direction Changer)

The direction of the bare optical fiber 3 that is drawn from the opticalfiber preform 2 in the downward vertical direction (first pathway L1) ischanged by 90 degrees by the first direction changer 20A, as a result,the direction of the bare optical fiber 3 is in the horizontal direction(second pathway L8).

The direction of the bare optical fiber 3 is changed by 90 degrees bythe second direction changer 20G, as a result, the direction of the bareoptical fiber 3 is in the upward vertical direction (third pathway L9).Furthermore, the direction of the bare optical fiber 3 is changed by 180degrees by the third direction changer 20H, as a result, the directionof the bare optical fiber 3 is in the downward vertical direction(fourth pathway L10).

The direction of the bare optical fiber 3, is changed by 90 degrees bythe fourth direction changer 201, as a result, the direction of the bareoptical fiber 3 is in the horizontal direction (fifth pathway L11). Thedirection of the bare optical fiber 3 is changed by 90 degrees by thefifth direction changer 20J, as a result, the direction of the bareoptical fiber 3 is in the downward vertical direction (sixth pathwayL12).

(Adjustment of Path Length of Bare Optical Fiber 3)

The measurement unit 50 measures an outer diameter of the optical fiberproduction intermediate 4 (i.e., an outer diameter of the coated layer)and outputs a measurement signal to the controller 150 based on themeasurement value.

The controller 150 controls the position in the vertical direction ofthe third direction changer 20H in accordance with the measurement valueof the outer diameter and thereby adjusts the path length of the bareoptical fiber 3.

According to the manufacturing method, since the path length of the bareoptical fiber 3 is adjusted by controlling the position in the verticaldirection of the third direction changer 20H, it is not necessary toensure a large space in the X-direction in which the direction changer20 is to be accommodated.

Accordingly, it is advantageous to reduce the manufacturing apparatus 1Ein size.

According to the manufacturing method, since it is possible to adjustthe temperature of the bare optical fiber 3 in the direction changers20A to 20J without varying the flow rate of the gas, it is possible toavoid the bare optical fiber 3 from being in contact with the inner sidesurface 21 c of the guide groove 21 due to a lack of flotation of thebare optical fiber.

EXAMPLES Example 1

The manufacturing apparatus 1A shown in FIG. 1 was prepared.

As the first direction changer 20A and the third direction changer 20C,the direction changer 201 shown in FIG. 3 was used.

As the second direction changer 20B, the direction changer 203 shown inFIG. 5 was used.

A width of the guide groove 21 was 145 μm.

A flotation turning radius of the bare optical fiber 3 was approximately62.5 mm.

Fluid which is to be introduced into the direction changers 20A and 20Bis air, and the temperature thereof was at a room temperature(approximately 24° C.).

The introduction flow rate of air into each of the first directionchanger 20A and the third direction changer 20C was 100 liters perminute. An introduction flow rate of air into the second directionchanger 20B was 200 liters per minute.

The first direction changer 20A was provided at the position at whichthe temperature of the bare optical fiber 3 becomes approximately 1000°C.

The bare optical fiber 3 (outer diameter of 125 μm) was obtained bydrawing the optical fiber from the optical fiber preform 2 in thedrawing unit 10.

As a drawing speed and a drawing tension, a common condition (drawingspeed of 30 m/second and a drawing tension of approximately 150 gf) wasadopted.

The direction of the bare optical fiber 3 that is drawn from the opticalfiber preform 2 in the downward vertical direction (first pathway L1) ischanged by the first direction changer 20A to be in the horizontaldirection (second pathway L2). Subsequently, the direction of the bareoptical fiber 3 is changed by 180 degrees by the second directionchanger 20B, as a result, the direction of the bare optical fiber 3 isin the direction (third pathway L3) opposite to the second pathway L2.Furthermore, the direction of the bare optical fiber 3 is changed by 90degrees by the third direction changer 20C, as a result, the directionof the bare optical fiber 3 is in the downward vertical direction(fourth pathway L4).

In the coating unit 30, the bare optical fiber 3 was subjected to acoating step using an ultraviolet curable resin, the UV lamp 40 airradiated the resin with ultraviolet light in the curing unit 40 andthereby a coated layer was cured, and the optical fiber 5 was obtained.

The optical fiber 5 passed through the pick-up unit 70 and the pulley 80and was wound around the winding unit 90.

The measurement unit 50 measured an outer diameter of the optical fiberproduction intermediate 4 (i.e., an outer diameter of the coated layer)and outputs a measurement signal to the controller 60 based on themeasurement value.

The controller 60 adjusted the path length of the bare optical fiber 3by controlling the position of the second direction changer 20B inaccordance with the measurement value of the outer diameter.

As a control method, PID control was used.

In the manufacturing method, flotation of the bare optical fiber 3 wasstabilized in the direction changers 20A to 20C.

In the manufacture of the optical fiber, a drawing velocity of theoptical fiber 5 varied at ±1 m/second; however, variation in the outerdiameter of the coated layer was within ±1 μm, and the diameter wasstabilized.

Thus, as a result of using the direction changers 20A to 20C, it wasdetermined that the optical fiber 5 can be manufactured with a highlevel of yield without damage to the bare optical fiber 3.

Example 2

The manufacturing apparatus 1B shown in FIG. 7 was prepared.

The pick-up unit 70 measured a drawing velocity of the optical fiber 5and carried out control such that: in the case where the drawingvelocity of the optical fiber 5 decreases, the second direction changer20B comes close to the first direction changer 20A and the thirddirection changer 20C; in the case where a drawing velocity of theoptical fiber 5 increases, the second direction changer 20B movesseparately from the first direction changer 20A and the third directionchanger 20C.

In this Example, the optical fiber 5 was manufactured under the controlcondition described above, and the condition other than theabove-described condition was the same as that of Example 1.

In the manufacturing method, flotation of the bare optical fiber 3 wasstabilized in the direction changers 20A to 20C.

In the manufacture of the optical fiber, a drawing velocity of theoptical fiber 5 varied at ±1 m/second; however, variation in the outerdiameter of the coated layer was within ±1 μm, and the diameter wasstabilized.

Thus, as a result of using the direction changers 20A to 20C, it wasdetermined that the optical fiber 5 can be manufactured with a highlevel of yield without damage to the bare optical fiber 3.

Example 3

The manufacturing apparatus 1D shown in FIG. 9 was prepared.

The direction changer 201 shown in FIG. 3 was used as the directionchangers 20A and 20F.

The direction changer 203 shown in FIG. 5 was used as the directionchangers 20B, 20D, and 20E.

The first direction changer 20A was provided at the position at whichthe temperature of the bare optical fiber 3 becomes approximately 800°C.

The bare optical fiber 3 (outer diameter of 125 μm) was obtained bydrawing the optical fiber from the optical fiber preform 2 in thedrawing unit 10.

As a drawing speed and a drawing tension, a common condition (drawingspeed of 40 m/second and a drawing tension of approximately 150 gf) wasadopted.

The direction of the bare optical fiber 3 that is drawn from the opticalfiber preform 2 in the downward vertical direction (first pathway L1) ischanged by 90 degrees by the first direction changer 20A to be in thehorizontal direction (second pathway L2). Subsequently, the direction ofthe bare optical fiber 3 is changed by 180 degrees by the seconddirection changer 20B, as a result, the direction of the bare opticalfiber 3 is in the direction (third pathway L3) opposite to the secondpathway L2. Furthermore, the direction of the bare optical fiber 3 ischanged by 180 degrees by the third direction changer 20D, as a result,the direction of the bare optical fiber 3 is in the direction (fourthpathway L5) opposite to the third pathway L3.

The direction of the bare optical fiber 3 is changed by 180 degrees bythe fourth direction changer 20E to be in the direction (fifth pathwayL6) opposite to the fourth pathway L5. Subsequently, the direction ofthe bare optical fiber 3 is changed by 90 degrees by the fifth directionchanger 20F to be in the downward vertical direction (sixth pathway L7).

In the coating unit 30, the bare optical fiber 3 was subjected to acoating step using an ultraviolet curable resin, the UV lamp 40 airradiated the resin with ultraviolet light in the curing unit 40 andthereby a coated layer was cured, and the optical fiber 5 was obtained.

The optical fiber 5 passed through the pick-up unit 70 and the pulley 80and was wound around the winding unit 90.

The measurement unit 50 measured an outer diameter of the optical fiberproduction intermediate 4 (i.e., an outer diameter of the coated layer)and outputs a measurement signal to the controller 130 based on themeasurement value.

The controller 130 adjusted the path length of the bare optical fiber 3by controlling the positions of the second direction changer 20B and thefourth direction changer 20E in accordance with the measurement value ofthe outer diameter.

As a control method, PID control was used.

In the manufacturing method, flotation of the bare optical fiber 3 wasstabilized in the direction changers 20A to 20F.

In the manufacture of the optical fiber, a drawing velocity of theoptical fiber 5 varied at ±1 m/second; however, variation in the outerdiameter of the coated layer was within ±1 μm, and the diameter wasstabilized.

Thus, as a result of using the direction changers 20A to 20F, it wasdetermined that the optical fiber 5 can be manufactured with a highlevel of yield without damage to the bare optical fiber 3.

Example 4

The manufacturing apparatus 1E shown in FIG. 10 was prepared.

The pick-up unit 70 measured a drawing velocity of the optical fiber 5and carried out control such that: in the case where the drawingvelocity of the optical fiber 5 decreases, the second direction changer20B and the fourth direction changer 20E come close to the directionchangers 20A, 20D, and 20F; in the case where a drawing velocity of theoptical fiber 5 increases, the second direction changer 20B and thefourth direction changer 20E move separately from the direction changers20A, 20D, and 20F.

In this Example, the optical fiber 5 was manufactured under the controlcondition described above, and the condition other than theabove-described condition was the same as that of Example 1.

In the manufacturing method, flotation of the bare optical fiber 3 wasstabilized in the direction changers 20A to 20F.

In the manufacture of the optical fiber, a drawing velocity of theoptical fiber 5 varied at ±1 m/second; however, variation in the outerdiameter of the coated layer was within ±1 μm, and the diameter wasstabilized.

Thus, as a result of using the direction changers 20A to 20F, it wasdetermined that the optical fiber 5 can be manufactured with a highlevel of yield without damage to the bare optical fiber 3.

Comparative Example 1

In this Comparative Example, an optical fiber 5 was manufactured underthe same condition as that of Example 1 except that the adjustment ofthe path length of the bare optical fiber 3 due to control of theposition of the second direction changer 20B is not carried out.

In the manufacturing method, it was determined that the outer diameterof the coated layer is varied at approximately ±5 μm, and stabilizedcoating cannot be realized.

Comparative Example 2

In this Comparative Example, an optical fiber 5 was manufactured underthe condition of Example 4 except that the adjustment of the path lengthof the bare optical fiber 3 due to control of the positions of thesecond direction changer 20B and the fourth direction changer 20E is notcarried out.

In the manufacturing method, it was determined that the outer diameterof the coated layer is varied at approximately ±5 μm, and stabilizedcoating cannot be realized.

In the above-description, a method of manufacturing an optical fiber ofthe invention and an optical fiber manufacturing apparatus thereof aredescribed; however, the technical scope of the invention is not limitedto the above embodiments, and various modifications may be made withoutdeparting from the scope of the invention.

What is claimed is:
 1. A method of manufacturing an optical fiber,comprising: preparing two fixed direction changers and a movabledirection changer located between the two fixed direction changers, eachof which comprises a guide groove and an outlet nozzle, the guide groovebeing configured to guide a bare optical fiber, the bare optical fiberbeing arranged along and introduced into the guide groove, the outletnozzle being formed in the guide groove and being configured to causethe bare optical fiber to float, one of the two fixed directionchangers, the movable direction changer, and the other of the two fixeddirection changers located in order from an upstream side to adownstream side in a fiber drawing direction from a drawing unit to acoating unit, the movable direction changer being movable in at leastone of a direction toward the two fixed direction changers and adirection away from the two fixed direction changers; drawing the bareoptical fiber from an optical fiber preform, thereby forming the bareoptical fiber; providing a coated layer made of a resin on a peripheryof the bare optical fiber; obtaining an optical fiber by curing thecoated layer; changing a direction of the bare optical fiber at aposition between: a position at which the bare optical fiber is formed;and a position at which the coated layer is provided on the periphery ofthe bare optical fiber, by use of the two fixed direction changers andthe movable direction changer; measuring a drawing velocity of theoptical fiber; and adjusting a length of the bare optical fiber from thedrawing unit to the coating unit by controlling a position of themovable direction changer so as to move in a direction toward positionsof the two fixed direction changers, based on a measurement value of thedrawing velocity, the drawing unit forming the bare optical fiber, thecoating unit providing the coated layer on the periphery of the bareoptical fiber; and moving the movable direction changer and therebystabilizing an outer diameter of the coated layer from increasing,control being carried out so that, when the drawing velocity of theoptical fiber decreases, the movable direction changer moves toward thetwo fixed direction changers, the movable direction changer is therebydisposed at a position closer to the two fixed direction changers, apath length of the bare optical fiber decreases accordingly, atemperature of the bare optical fiber which is to be introduced into thecoating unit relatively increases, a thickness of the coated layerformed in the coating unit decreases, the outer diameter of the coatedlayer decreases.
 2. The method according to claim 1, further comprising:preparing a controller and a measurement unit, the measurement unitbeing capable of measuring the drawing velocity of the optical fiber andbeing configured to output a measurement signal to the controller basedon the measurement value output from the measurement unit, wherein thecontroller controls a position of the movable direction changer based onthe measurement signal output from the measurement unit and therebyadjusts the length of the bare optical fiber from the drawing unit tothe coating unit.
 3. A method of manufacturing an optical fiber,comprising: preparing two fixed direction changers and a movabledirection changer located between the two fixed direction changers, eachof which comprises a guide groove and an outlet nozzle, the guide groovebeing configured to guide a bare optical fiber, the bare optical fiberbeing arranged along and introduced into the guide groove, the outletnozzle being formed in the guide groove and being configured to causethe bare optical fiber to float, one of the two fixed directionchangers, the movable direction changer, and the other of the two fixeddirection changers located in order from an upstream side to adownstream side in a fiber drawing direction from a drawing unit to acoating unit, the movable direction changer being movable in at leastone of a direction toward the two fixed direction changers and adirection away from the two fixed direction changers; drawing the bareoptical fiber from an optical fiber preform, thereby forming the bareoptical fiber; providing a coated layer made of a resin on a peripheryof the bare optical fiber; obtaining an optical fiber by curing thecoated layer; changing a direction of the bare optical fiber at aposition between: a position at which the bare optical fiber is formed;and a position at which the coated layer is provided on the periphery ofthe bare optical fiber, by use of the two fixed direction changers andthe movable direction changer; measuring a drawing velocity of theoptical fiber; and adjusting a length of the bare optical fiber from thedrawing unit to the coating unit by controlling a position of themovable direction changer so as to move away from positions of the twofixed direction changers, based on a measurement value of the drawingvelocity, the drawing unit forming the bare optical fiber, the coatingunit providing the coated layer on the periphery of the bare opticalfiber; and moving the movable direction changer and thereby stabilizingan outer diameter of the coated layer from decreasing, control beingcarried out so that, when the drawing velocity of the optical fiberincreases, the movable direction changer moves away from the two fixeddirection changers, the movable direction changer is thereby disposed ata position farther apart from the two fixed direction changers, a pathlength of the bare optical fiber increases accordingly, a temperature ofthe bare optical fiber which is to be introduced into the coating unitrelatively decreases, a thickness of the coated layer formed in thecoating unit increases, the outer diameter of the coated layerincreases.
 4. The method according to claim 3, further comprising:preparing a controller and a measurement unit, the measurement unitbeing capable of measuring the drawing velocity of the optical fiber andbeing configured to output a measurement signal to the controller basedon the measurement value output from the measurement unit, wherein thecontroller controls a position of the movable direction changer based onthe measurement signal output from the measurement unit and therebyadjusts the length of the bare optical fiber from the drawing unit tothe coating unit.